This question already has an answer here:
I've been reading through this forum and google for this answer for a while now, the closest I have come to my answer is the thread linked above. Specifically this answer here. https://boardgames.stackexchange.com/a/12216/18889
Opponent attacks with Long Tusk without pumping it up, leaving it at 2/2. I do not declare any blockers. Opponent decided to pay energy to make it a 3/3. In response, I cast shock.
Does shock take effect, since its an instant, before Long Tusk becomes a 3/3?
Thanks for the help in advanced.